1. Field of Invention
The invention relates to an image display system and an image display method, and, in particular, to an image display system having a light source and an image display method of controlling the light source.
2. Related Art
An active matrix liquid crystal display (LCD) apparatus has been widely applied to an image display system due to its low power consumption, small thickness and better color displaying properties.
A LCD apparatus mainly includes a thin-film transistor (TFT) substrate, a liquid crystal layer and a color filter substrate. A plurality of pixels is also defined in the LCD apparatus. Each pixel includes red, green and blue sub-pixels. The color filter substrate has a plurality of red, green and blue filter layers respectively serving as portions of the red, green and blue sub-pixels. The TFT substrate has a plurality of pixel electrodes and a plurality of TFTs serving as switches. The color filter substrate has a common electrode. The pixel electrode and the common electrode form a liquid crystal storage capacitor. The TFT is driven by a scan line driving circuit so that a data line driving circuit can write data into the liquid crystal storage capacitor to control liquid crystals in the liquid crystal layer to rotate.
A backlight module uses a white-light source, such as a cold cathode fluorescent lamp (CCFL) or a white-light diode. The white light passes through a polarizer on the TFT substrate, the liquid crystal layer having the liquid crystals controlled to rotate, various color filter layers with different colors, and a polarizer on the color filter substrate so that different colors may be represented and an image may be generated.
Generally speaking, as shown in FIG. 1, the national television system committee (NTSC) ratio of the LCD apparatus is about 70%. Herein, the NTSC ratio represents the ratio of the gamuts that can be displayed by the LCD apparatus based on the conventional cathode ray tube (CRT) display under the CIE 1931 specification. That is, the CRT display corresponds to the NTSC ratio of 100%. As the NTSC ratio gets higher, the display ability is closer to that of the conventional CRT display and more colors may be represented, and the displayed color thereof is also closer to the true color of the original object, and the image quality is thus better and less distortion may occur.
In the LCD apparatus, however, the white light passing through the green filter layer cannot approach the pure green color so that the NTSC ratio cannot be easily enhanced, and the image quality cannot be effectively enhanced. In order to increase the NTSC ratio to enhance the image quality, the thickness of the filter layer is increased in the prior art so that the white light after being filtered can be closer to the pure color of the filter layer. Consequently, the image brightness is lowered although the NTSC ratio is increased. Thus, the image quality cannot be effectively enhanced.
Therefore, it is an important subject to provide an image display system and an image display method to solve the above-mentioned problems.